How to test MS3X injector drivers?

[hobieboy]

Hi guys,
I am running into a situation where feeling seems to go crazy whenever PW is below ~2.9ms - engine will start to buck (RPM drops, MAP goes towards atmospheric), AFR goes lean, PW increases (per VE table) then engine catches. I am suspecting it is either an injector or injector driver issue.

So, like to find out how could I test if the drivers are working 100%?

I tried test mode & did hear each injector clicks but can there be a situation where the driver only works on certainly PW range?

thanks!

[jsmcortina]

Best to flow test the injectors using test mode. See how they behave at low PW.

James

[hobieboy]

Thanks for the suggestion James. Will try that & hope I have good news to report.

[hobieboy]

While I was setting up the test it occurred to me that with the engine not running, there is no way for me to establish the fuel pressure - I rely on MS3/TS to get that from the sensor and I am trying to use the actual fuel rail/pump/etc from the car to recreate as realistic a scenario.

So, whatever fuel volume I measure is really meaningless? I can only really ascertain at low PW, is each injector firing...

Is there any cheap setup that anyone used before? If I have to build an elaborate test rig with fuel pressure gauge, pressure regulator, etc. then I may as well send the injectors out for test

[billr]

If your fuel pump control is simple "on/off" (runs full-power when engine is running), then no problem; you can "manually" turn on the pump in the injector test-mode menu.

If, though, you are using PWM of the pump, like in a "return-less" system, then it gets more complicated. There are several threads here pertaining to that. I found the easiest way is to give the MS a tachin signal with a test wheel/sensor. Maybe a Stim could be used?

[hobieboy]

My fuel pump is a simple on/off type. I can turn it on/off via MS test mode without issue. But I still can't be sure of the actual fuel pressure?

[billr]

You will have to have a mechanical gauge or a pressure transducer to verify fuel pressure; either can be had for about the cost of one injector. However, you don't really need to know the pressure to get meaningful data. All that matters is that the pressure you test with is the same as the pressure you run the engine with. Of course, knowing the pressure now, while testing, will save wonderment if you run into problems in the future. You can check pressure then and see if it has drifted from now.

I urge you to invest in a fuel-pressure sensor. That pressure is so important and there are so many ways it can be off (FPR, pump itself, filter, tank empty, etc.), that it is nice to be able to look at a log and quickly know the FP is either OK or not. One item to get "off the list" if you run into problems...

[hobieboy]

Well, it turned out to be easier than I thought... I have a leaky injector

As soon as I fab up some very crude temporary set up and pressurized the fuel rail, fuel started leaking from the suspected faulty injector. I turned the pump off & even disconnect the battery (I have a quick disconnect ), a small cup of fuel continued to leak out - residual from the fuel rail.

I do have a fuel pressure sensor installed but as I said its a sensor, not a gauge so I can only read the output when MS is active. When I enabled test mode, I don't think I can see the fuel pressure reading.

[hobieboy]

Wanted to also add... I also wanted to do the test as close to a real running situation as I can - using same fuel pump, rail, harness, etc so that I can truly test functionality as well as flow rate hence my other reluctance to build a separate test rig outside of the engine bay.

[billr]

In test mode all the sensor readings are active, you can see that FP from your sensor if you put up a "gauge" on the dash screen.

[hobieboy]

ah - didn't know that but make sense... the test mode window was big enough to cover most of the gauges underneath so I never notice. Learn something new everyday